铂载钴钼二元硫化物对H_2S电催化活性研究

Electro-catalytic activities of Co-Mo sufides coated on platinum electrode for H_2S

为考察溶胶凝胶法制备的Co-Mo二元硫化物对H_2S气体的电催化活性,通过循环伏安法和Tafel曲线分析对铂载不同Co、Mo掺杂比的电催化剂进行表征。结果表明,不同阳极电催化剂交换电流密度J0由大到小依次为,铂载n(Co):n(Mo)=2:3、铂载n(Co):n(Mo)=2:1、铂载n(Co):n(Mo)=1:1和铂,即铂载n(Co):n(Mo)=2:3阳极电催化剂具有较好的活性,这与循环伏安曲线测试结果一致。电解质溶液pH值为6～7时,随着温度的升高铂载n(Co):n(Mo)=2:3阳极电催化剂活性呈现上升的趋势。优化后的Co、Mo掺杂原子比约为0.66,此类电催化剂在操作温度80℃下,交换电流密度为1.318mA/cm^2,表观活化焓值为616.6 kJ/mol。研究表明,铂载钴钼二元硫化物适合作为低温H_2S燃料电池阳极电催化剂,其中Co、Mo掺杂比对电催化活性影响较大。

This article is dedicated to present sol-gel method for preparing precumor powder of Co-Mo binary sulfides as anode catalysts, which can then be vulcanized in H2S atmosphere. While investigating the electro-catalytic activity of these anode catalysts in different Co-Mo ratios coated on platinum, the cyclic voltammetry （CV） method and Tafel eurve method were applied to test the validity of the catalysts. As a corrosive, noxious gaseous pollutant with unpleasant smell, H2S has been recently utilized as fuel gas fed into anode chamber of fuel cell to recover electric energy. Experimenting with the various anode materials in hoping to obtain those with good electro-catalytic activities, and then comparing the peak current （lpcak） obtained from CV curve, a conclusion have been reached that the experimental results are in qualitative conformity with the descriptive data of the different corresponding anode catalysts, which can be ordered as follows： n（Co） ： n（Mo） = 2：3 coated on platinum 〉 n（Co） ： n（Mo） = 2：1 coated on platinum 〉 n（Co） ： n（Mo） = 1 ： 1 coated on platinum 〉 Pt. The above comparison also indicates that anode catalyst, rt（Co） ： n（Mo） = 2：3 coated on platinum can be chosen as the best one for the electro-catalytic activity. Furthermore, the anode catalyst activity tends to become better at higher temperatures, when pH = 6 - 7 in the electrolyte solution. On the other hand, the exchange current density （J0） obtained from Tafel curve confirms the aforementioned facts quantitatively. As a result, the optimized Co-Mo ratio of anode catalysts should be about 0.66. At the operating temperatures for fuel ceils, for example, at 80 ℃, the J0 value of optimized anode catalyst is expected to reach 1.318 mA/cm^2, while apparent activation enthalpy, △rH^＊ , can also be as low as 616.6 kJ/mol. This means that lower activation energy is needed when H2S is electrochemically oxidized on the optimized anode catalyst. In addition, Co-Mo binary sulfides can also be used as anode catalysts when H2S is electrolyzed or electrochemically oxidized, and the optimized Co-Mo ratio can be obtained before coated on the platinum. Further research remains needed to analyze the electron and total conductivity of the anodes as fuel cells.